sophy - Sophia數據庫的快速Python綁定

sophy - Sophia數據庫的快速Python綁定。 Sophia Database v2.1.

特性:

• Append-only MVCC database
• ACID transactions
• Consistent cursors
• Compression
• Multi-part keys
• Ordered key/value store
• Range searches
• Read-only views of point-in-time
• Prefix searches
• Python 2.x and 3.x

Limitations:

• Not tested on Windoze.

The source for sophy is hosted on GitHub

If you encounter any bugs in the library, please open an issue, including a description of the bug and any related traceback.

Installation

The sophia sources are bundled with the sophy source code, so the only thing you need to install is Cython. You can install from GitHub or from PyPI.

Pip instructions:

$ pip install Cython sophy

Git instructions:

$ pip install Cython
$ git clone https://github.com/coleifer/sophy
$ cd sophy
$ python setup.py build
$ python setup.py install

Usage

Sophy is very simple to use. It acts primarly like a Python dict object, but in addition to normal dictionary operations, you can read slices of data that are returned efficiently using cursors. Similarly, bulk writes using update() use an efficient, atomic batch operation.

To begin, instantiate your Sophia database. Multiple databases can exist under the same path:

>>> from sophy import connect
>>> db = connect('data-dir', 'db-name')

We can set values individually or in groups:

>>> db['k1'] = 'v1'
>>> db.update(k2='v2', k3='v3', k4='v4')  # Efficient, atomic.
>>> with db.transaction() as txn:  # Same as .update()
...     txn['k1'] = 'v1-e'
...     txn['k5'] = 'v5'
...

We can read values individually or in groups. When requesting a slice, the third parameter (step) is used to indicate the results should be returned in reverse. Alternatively, if the first key is higher than the second key in a slice, sophy will interpret that as ordered in reverse.

>>> db['k1']
'v1-e'
>>> [item for item in db['k2': 'k444']]
[('k2', 'v2'), ('k3', 'v3'), ('k4', 'v4')]

>>> list(db['k3':'k1'])  # Results are returned in reverse.
[('k3', 'v3'), ('k2', 'v2'), ('k1', 'v1-e')]

>>> list(db[:'k3'])  # All items from lowest key up to 'k3'.
[('k1', 'v1-e'), ('k2', 'v2'), ('k3', 'v3')]

>>> list(db[:'k3':True])  # Same as above, but ordered in reverse.
[('k3', 'v3'), ('k2', 'v2'), ('k1', 'v1-e')]

>>> list(db['k3':])  # All items from k3 to highest key.
[('k3', 'v3'), ('k4', 'v4'), ('k5', 'v5')]

Values can also be deleted singly or in groups. To delete multiple items atomically use the transaction() method.

>>> del db['k3']
>>> db['k3']  # 'k3' no longer exists.
Traceback (most recent call last):
  ...
KeyError: 'k3'

>>> with db.transaction() as txn:
...     del txn['k2']
...     del txn['k5']
...     del txn['kxx']  # No error raised.
...
>>> list(db)
[('k1', 'v1-e'), ('k4', 'v4')]

Transactions

>>> with db.transaction() as txn:
...     txn['k2'] = 'v2-e'
...     txn['k1'] = 'v1-e2'
...
>>> list(db[::True])
[('k4', 'v4'), ('k2', 'v2-e'), ('k1', 'v1-e2')]

You can call commit() or rollback() inside the transaction block itself:

>>> with db.transaction() as txn:
...     txn['k1'] = 'whoops'
...     txn.rollback()
...     txn['k2'] = 'v2-e2'
...
>>> list(db.items())
[('k1', 'v1-e2'), ('k2', 'v2-e2'), ('k4', 'v4')]

If an exception occurs in the wrapped block, the transaction will automatically be rolled back.

Cursors

Sophia is an ordered key/value store, so cursors will by default iterate through the keyspace in ascending order. To iterate in descending order, you can specify this using the slicing technique described above. For finer-grained control, however, you can use the cursor() method.

The Database.cursor() method supports a number of interesting parameters:

• order: either '>=' (default), '<=' (reverse), '>' (ascending not including endpoint), '<' (reverse, not including endpoint).
• key: seek to this key before beginning to iterate.
• prefix: perform a prefix search.
• keys: include the database key while iterating (default True).
• values: include the database value while iterating (default True).

To perform a prefix search, for example, you might do something like:

>>> db.update(aa='foo', abc='bar', az='baze', baz='nugget')
>>> for item in db.cursor(prefix='a'):
...     print item
...
('aa', 'foo')
('abc', 'bar')
('az', 'baze')

Configuration

Sophia supports a huge number of configuration options, most of which are exposed as simple properties on the Sophia or Database objects. For example, to configure a Sophia database to use mmap and compression:

>>> env = Sophia('my/data-dir', log_path='my/log-dir', threads=4)
>>> db = env.database('my-db', mmap=True, sync=True, compression='zstd')

You can also force checkpointing, garbage-collection, and other things using simple methods:

>>> db.checkpoint()
>>> db.gc()

Some properties are read-only:

>>> db.index_count
10
>>> len(db)
10
>>> db.status
'online'
>>> db.memory_used
69

Take a look at the configuration docs for more details.

項目地址： https://github.com/coleifer/sophy